Connector

ABSTRACT

A connector comprising at least one pair of apertures for receiving a fastener, such as a screw, a load bearing filament extending continuously along a predefined circuitous path which extends between and around each of the apertures of said pair of apertures. The load bearing filament extends around each aperture to define multiple aperture forming strands of said load bearing filaments. The multiple aperture forming strands of the load bearing filament are bound together around each aperture by binding filaments in order to constrain relative lateral movement between the aperture forming multiple strands and to define the shape of each aperture.

FIELD OF THE INVENTION

The present invention concerns a connector, in particular but notexclusively, a connector for use in surgery for connecting bones or boneparts to one another.

BACKGROUND OF THE INVENTION

When connecting bones or bone parts to one another using a connector, itis desirable for the connector to be capable of transmitting loadsbetween the connected bone parts in a predetermined manner. This may bedone to constrain separation between the bone parts by a predeterminedamount and also constrain to a predetermined amount, the amount oftorsional movement between the bone parts.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided aconnector comprising at least one pair of apertures for receiving afixation means, such as a screw or a toggle, a load bearing filamentextending continuously along a predefined circuitous path which extendsbetween and around each of the apertures of said pair of apertures, saidload bearing filament extending around each aperture to define multipleaperture forming strands of said load bearing filaments, said apertureforming multiple strands of said load bearing filament being boundtogether around each aperture by binding filaments in order to constrainrelative lateral movement between said aperture forming multiple strandsand to define the shape of each aperture.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic plan view of a connector according to a firstembodiment of the present invention;

FIGS. 2 a to 2 c are diagrammatic plan views of modifications to thefirst embodiment of the present invention;

FIG. 3 is a diagrammatic plan view of a connector according to a secondembodiment of the present invention;

FIG. 4 diagrammatically illustrates a first example of formation of thesecond embodiment;

FIG. 5 is a diagrammatic plan view of a third embodiment of the presentinvention;

FIG. 6 is a diagrammatic plan view of a fourth embodiment of the presentinvention;

FIG. 7 is a diagrammatic illustration of connectors according to thepresent invention.

FIG. 8 is a second example of formation of the second embodiment; and

FIGS. 9 a to 9 d schematically illustrate laying of load bearingfilaments to form multiple aperture forming strands.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, there is shown a connector 500 accordingto a first embodiment of the present invention.

The connector 500 includes a pair of apertures 18 a , 18 b and a loadbearing filament 28 which follows a circuitous path which extendscontinuously around and between the apertures 18 a , 18 b . In use, theconnector is attached to say a pair of bone parts by a fixation means,such as a screw or a toggle, located in the apertures 18 a, 18 b.

The filament 28 is preferably laid along said circuitous path for aplurality of complete circuits so as to define multiple strands 28 a ,28 b and 28 c.

In FIG. 1, the multiple strands 28 a define aperture connecting strandswhich extend in a direction parallel to the central axis C_(L) joiningthe pair of apertures 18 a , 18 b ; strands 28 b define aperture formingstrands which extend continuously around each aperture 18 a, 18 b; andstrands 28 c define aperture connecting strands which extend diagonallybetween the apertures 18 a , 18 b.

As indicated in FIG. 2 a, 2 b and 2 c the circuitous path may be variedin order to change the configuration of the connector 500.

In FIG. 2 a, the diagonal strands 28 c are omitted such that theapertures 18 a , 18 b defined by the strands 28 b are connected bystrands 28 a only.

Alternatively, as indicated in FIG. 2 b, strands 28 a are omitted suchthat strands 28 b are connected by diagonal strands 28 c only.

In the embodiment of FIG. 2 c, strands 28 b only partially extend aroundthe outer periphery of each aperture 18 a, 18 b.

With this embodiment, strands 28 a may also be included such thatapertures 18 a , 18 b are connected by strands 28 a and 28 c ; oralternatively strands 28 a may be provided instead of strands 28 c.

Binding filaments 30 are provided which secure the strands 28 b togetherin order to constrain relative movement therebetween around eachaperture 18 a, 18 b and also define the shape of each aperture 18 a, 18b.

The binding filaments 30 thereby act to maintain integrity of eachaperture 18 a , 18 b when a fixation means, such as a bone screw, is tobe inserted through the aperture during attachment of the connector; thebinding filaments 30 also act to maintain integrity of each aperture 18a, 18 b when a tensile load is applied between the apertures 18 a , 18 bduring use.

Accordingly, a bone screw may be inserted directly into apertures 18 a,18 b without the need for an intermediary support such as a washer orcollar.

In the embodiments of FIGS. 1, 2 a and 2 b the binding filaments 30preferably extend around the entire periphery of each aperture 18 a , 18b.

In the embodiment of FIG. 2 c, the binding filaments 30 extend about theouter periphery only of the apertures 18 a , 18 b.

In FIG. 3 a further embodiment 600 is illustrated which comprises afirst pair of apertures 18 a , 18 b linked with a second pair ofapertures 18 b, 18 c. The apertures 18 a, 18 b; 18 b, 18 c in each pairare connected to one another and defined by the load bearing filament28. As with the first embodiment, the load bearing filament 28 extendsalong a circuitous path between and around the apertures 18 a, 18 b and18 c so as to connect them by multiple strands 28 a and/or 28 c anddefine them by strands 28 b. In the embodiment illustrated in FIG. 3,strands 28 a only are provided.

Preferably the circuitous path along which the load bearing filament 28extends enables the strands 28 a (and/or 28 c if provided) to be severed(as indicated by line S_(v)) between one pair of apertures 18 b , 18 cwithout adversely affecting the connection between the other pairs ofapertures 18 a , 18 b.

The connection defined by the load bearing filament 28 between each pairof apertures may thus be considered as a chain defined by a series ofchain links.

An illustration of a circuitous path for the load bearing filament 28 inorder to form the embodiment 600 is illustrated in FIG. 4.

The starting point of the path is S_(p) and the finishing point isF_(p). The load bearing yarn 28 is laid along the path in the directionindicated by the arrows.

Initially the filament is laid partially around the periphery ofaperture 18 a , then extends to and completely around aperture 18 b thenextends to and completely around aperture 18 c and then extends to andaround aperture 18 b . It then extends to and completely round aperture18 a.

This produces single strands 28 a and multiple strands 28 b.

If desired the load bearing yarn 28 may be laid along this circuitouspath several times in order to provide multiple strands 28 a.

The multiple strands 28 b are secured together by binding filaments 30after the load bearing filament 28 has been laid along the circuitouspath.

An alternative circuitous path for forming the embodiment 600 of FIG. 4is illustrated in FIG. 8.

Initially the filament 28 is laid partially around the periphery of 18 a, then extends to and partially around the aperture 18 a . Thus thefilament 28 initially follows a first substantially elliptical pathwhich extends about apertures 18 a , 18 b. The filament 28 is repeatedlylaid along the first elliptical path for a predetermined number of timesso as to define multiple strands 28 a and multiple strands 28 b. Thesecollectively form a first chain link or loop L₁.

After the filament 28 has been laid along the first elliptical path forsaid predetermined number of times, it is then laid along a secondsubstantially elliptical path for another predetermined number of times;the second elliptical path extending around the next pair of apertures18 b, 18 c. This forms a second chain link or loop L₂.

After completing laying of the filament 28 around the second ellipticalpath for said predetermined number of times, the filament 28 is laidalong side the strand of the first elliptical path which extend betweenapertures 18 a, 18 b. In this way, the same number of strands 28 a arelaid inbetween each pair of apertures 18 a, 18 b; and 18 b; 18 c.

After laying of the load bearing filament 28, the multiple apertureforming strands 28 b are secured together by binding filaments 30 whichextend around each aperture (as shown in broken lines).

When the surgical connector includes multiple strands 28 a or 28 c, itis important that the tensile loads inbetween a pair of anchorageapertures be shared as equally as possible between the individualstrands making up each multiple strand 28 a, and/or 28 c.

This is particularly important when, in use, the apertureinterconnecting strands 28 a, and/or 28 c, extend between a pair ofapertures located on different planes which are also possibly ofdifferent orientation.

In order to achieve, as best as possible an equal sharing of tensileloads in each individual strand which makes up a multiple apertureinterconnecting strand 28 a, and/or 28 c, the filament 28 when beinglaid along the circuitous path is anchored at selected anchoragelocations A_(L) to a support backing sheet MS so that each individualstrand extends between a series of anchorage locations spaced along itslength and so is constrained thereby to follow a predefined path.

Preferably the filament is laid along the circuitous path by anembroidery machine having a base cloth support table movable in twodimensions in response to a patterning control for accuratelypositioning the base cloth relative to the sewing needle of the machine.The sewing needle is positioned on one side of the base cloth (referredto as the needle side of the base cloth) and when actuated penetratesthrough the base cloth to project from the opposite side of the basecloth (referred to as the looper side) in order to co-operate with alooper which supplies a looper thread to form a sewn stitch with threadsupplied by the needle.

Preferably, the filament 28 is supplied as the looper thread and so islaid on the looper side of the base cloth. The stitches formed betweenthe filament 28 and needle thread define the anchorage locations alongthe length of the filament.

As illustrated in FIGS. 9 a to 9 c the thread S_(T) supplied to thesewing needle is preferably chosen so as to be much finer than thefilament 28 such that the filament 28 remains substantially flat withthe base cloth and is not pulled through toward the needle side of thebase cloth. In this way the filament 28 remains substantially straightbetween each adjacent anchorage location defined by the stitches.

The length of the filament 28 inbetween each adjacent stitch istherefore accurately predetermined.

It will be appreciated that as an alternative, the heavier load bearingfilament 28 could be supplied by the needle and the finer thread S_(T)be supplied by the looper.

Preferably a minimal number of stitches are formed along the filament 28defining the aperture interconnecting strands 28 a and/or 28 c.

When laying the filament 28 around an aperture, the anchorage locationsare arranged to define a polygonal path (see FIG. 9). The number ofanchorage locations A_(L) and the spacing between adjacent locations arechosen, bearing in mind the diametric size of the aperture to be formedand the bending capability of the filament 28.

It is envisaged that the number of anchorage locations around anaperture is at least 3.

In addition to laying the filament 28 to define predetermined lengthsinbetween adjacent anchorage locations, the anchorage locations foradjacent individual strands 28 b around the aperture to be formed arepositioned such that adjacent strands are nested in contact together ina predefined manner to resist lateral movement of the strands 28 brelative to one another when a tensile load is applied between a pair ofadjacent apertures.

In addition, all the individual strands 28 b extending about a givenaperture are bound together by sewn stitches formed from bindingfilaments 30. Preferably the binding filaments 30 are sewn in a zig-zagmanner around each aperture so as to enclose the strands 28 b.

In this way, in use, the strands 28 b remain in substantially the sameposition relative to one another as when they were laid and so eachretains a predefined position around the aperture and so all individualstrands making up the multiple aperture interconnecting strands 28 aand/or 28 c also retain their predefined length when placed under atensile load inbetween adjacent apertures 18 and so the tensile load issubstantially equally shared by the individual aperture interconnectingstrands.

As shown in FIGS. 9 b, 9 c, the anchorage locations around A_(L) theaperture to be formed for one strand 28 b are off-set from the anchoragelocations of the neighbouring strand 28 b. This enables the strands 28 bto be closely arranged.

Preferably, as shown in FIG. 9 d, the individual strands 28 b may bearranged on top of one another such that a strand 128 b is seated withina groove 129 formed inbetween a pair of adjacent strands 228 b. In thisway, it is possible to stack strands 28 b on top of one another in adisciplined and predefined manner to obtain a relatively large number ofnested strands in a relatively small space which co-operate with oneanother to resist relative lateral movement.

When stacking strands of filament 28 on top of one another, it ispreferred to lay the strands closer to the aperture first and thensuccessively lay strands on the outer side of the laid strands. Thisenables strands to be laid upon one another without reducing the desireddiameter of the aperture.

In the embodiment illustrated in FIG. 1, the load bearing filament 28 issupported on a backing sheet MS which is preferably a mesh-like fabricformed from interconnected sewn stitches formed from yarns 20.

The backing sheet MS primarily serves the purpose of retaining the loadbearing filament 28 in a disciplined fashion for facilitating handlingof the connector during implantation; it is not intended to accommodatetensile loadings between adjacent apertures. Accordingly, yarns 20 maybe of a lighter weight than the filament 28.

As discussed above, the sewn stitches are preferably formed usingembroidery techniques which produce stitches above and below the loadbearing filament 28 and so enwrap the load bearing filament 28 withinthe mesh-like fabric. Normally the embroidery will be performed on abase cloth which may be soluble so as to enable the base cloth to bedissolved away prior to implantation. In such a case, the sewn stitchesdefining the mesh-like fabric then constitute the backing sheet.

Alternatively, the base cloth may be retained to define the backingsheet MS, this may be a knitted or woven fabric or a sheet of materialsuch as plastics to which the load bearing filament 28 is attached, byfor example suitable stitching. The backing sheet MS whether formed by asheet or a mesh-like fabric, or a knitted or woven fabric may bedissolvable so that once the backing sheet MS dissolves away it leavesapertures 18 a , 18 b connected solely by the load bearing filaments.

The load bearing filaments may be laid along the circuitous path bypassing around pegs 70 (illustrated in FIGS. 2 c) with the strands 28 bthen being subsequently secured by either stitching filaments 30 orwrapping filaments 30 around the strands 28 b (eg. using whippingtechniques).

The load bearing filament 28 may be a textile yarn such as a polyesterbraided thread as used for sutures. Preferably the suture thread has adiametric size between 0.2 to 0.5 mm, preferably about 0.35 mm. Othertypes of yarn could also be used, for example polypropylene,polyethylene, polyamide.

Preferably, the number of strands making up the multiple strands 28 z,28 b and/or 28 c vary between 2 to 15; more preferably vary between 5 to10.

Instead of a textile yarn, other types of filamentary material may beused, e.g. wire of suitable metals such as a SMA (Shape Memory Alloy),aramid fibres, glass strands.

The load bearing yarn may be formed from a material which slowlydissolves after implantation. Suitable examples are polylactic acid oralginate fibres.

In general it is envisaged that any filament having the desired loadbearing capabilities and flexibility for bending to lie along thedesired circuitous path may be used.

Preferably, the yarn 20 and/or binding filament 30 is a textile yarn,preferably a polyester braided thread. The yarn 20 and/or bindingfilament 30 is preferably a suture braid thread having a diametric sizebetween 0.1 to 0.2 mm, preferably about 0.15 mm.

It will be appreciated that the principle of connecting adjacent pairsof apertures 18 a, 18 b by laying a load bearing filament 28 along acircuitous path enables many different types of connector to beconstructed which are of the desired shapes and sizes tailored for aparticular application.

As indicated in broken lines in FIG. 3, it is envisaged that theconnector of the invention may incorporate a pulling tail or cord P_(T)which is longitudinally aligned with the row of apertures 18 a, 18 b and18 c.

In use, a surgeon is able to secure the connector using aperture 18 aand then pull on the pulling tail P_(T) in order to tension theconnector before securing the connector using apertures 18 b and/or 18c. The connector is therefore pre-tensioned before final fixing.

Preferably the pulling tail P_(T) is formed by a plurality of strands ofload bearing yarn 28 which are laid so as to form a continuation of thechain formation. After installation the pulling tail P_(T) may be cutaway. Alternatively, the pulling tail may be used as a tie for providingadditional anchorage of the connector.

By way of example, in FIG. 5 a connector 300 suitable for attachment toa vertebrae is illustrated.

In connector 300, the load bearing filament 28, in effect, creates achain-link between apertures 18 a, 18 b and a pair of chain linksbetween apertures 18 b, 18 c and 18 b, 18 d. This means that loads arespread evenly from aperture 18 b to both apertures 18 c, 18 d.

Aperture 18 c is connected to three apertures 18 b, 18 d and 18 e bychain-links defined by strands 28 a such that loads are evenlydistributed from aperture 18 c to apertures 18 b, 18 d and 18 e.

A further example is illustrated in FIG. 6 which is a connector 400suitable for use as an anterior spinal plate.

The connector 400 includes six arms 401 each formed by a series ofapertures 18 interconnected by chain-links formed by the filaments 28.The arms 401 radiate from three main fixation apertures 18 a, 18 b and18 c. These apertures 18 a, 18 b and 18 c are attached to the LSvertebra of a patient and the arms 401 are attached to the sacrum. Dueto the multiplicity of arms 401 and the plurality of apertures 18 theycontain, it is possible to obtain good anchorage on the complex, threedimensional shape of the sacrum.

Preferably, as shown in FIG. 6, the end aperture 18 d of each of theouter pair of arms 401 is preferably interconnected to at least two ofthe apertures 18 a–18 c in order to provide a desired spread ofloadings.

A specific use of connectors according to the present invention isillustrated in FIG. 7 wherein the connector is used as a spinalstabilisation device. In FIG. 7, the connector 800 is shown as beingconnected to two vertebrae V₁, V₂ by four pedicle screws 801, 802, 803and 804. It will be seen that the pairs of screws 801, 802 and 803, 804located on opposite sides of the vertebrae are each linked by flexibleconnectors 807 and that they are also linked by transverse connectors808.

It is to be appreciated that in the connector of the present invention,the load bearing filament 28 is laid along a predefined circuitous pathto define adjacent individual strands 28 b extending about each aperturewith aperture connecting strands 28 a and/or 28 c extending inbetweenadjacent apertures.

The individual strands 28 b are laid in a nested arrangement withindividual strands held in the nested arrangement at anchorage locationsconnected to a backing sheet and by binding filaments 30 which bind allthe individual strands 28 b together. Collectively securance ofindividual strands 28 b at said anchorage locations and binding all thestrands 28 b together by filaments 30 serve to restrain relative lateralmovement between the individual strands 28 b when a tensile load isapplied between a pair of adjacent apertures. Accordingly, the primepurpose of the anchorage locations and binding filament 30 is tomaintain the strands 28 b in position and not, themselves, toaccommodate the tensile loadings inbetween adjacent apertures.

Accordingly the binding filament 30 and needle sewing thread used forforming the anchorage locations can be of a lighter weight than the loadbearing filament 28. Since the binding filament 30 and sewing thread donot form a tensile load bearing function, the bulk size of the connectoris, in the main, determined by the amount of load bearing filament 28required.

This enables the connector of the present invention to be of arelatively small size compared to other known connectors.

Also, since the backing sheet is provided primarily to retain the loadbearing strands, in particular strands 28 a, 28 c in a disciplinedmanner for handling purposes during implantation, the flexibility ofstrands 28 a, 28 c is not impeded by the relatively lightweight backingsheet and thereby enables the load bearing strands 28 a, 28 c tobend/flex in a smooth manner inbetween adjacent bone anchoragelocations.

1. A connector comprising at least one pair of apertures for receiving afastener, a backing sheet, and at least one load bearing filamentextending continuously along a predefined circuitous path which extendsbetween and at least partially around each of said pair of apertures,said load bearing filament including multiple aperture forming strandsextending around each aperture, said multiple aperture forming strandsof said load bearing filament being supported on said backing sheet andbound together at least partially around each aperture by sewn stitchesformed from binding filaments in order to constrain relative lateralmovement between said aperture forming multiple strands and to definethe shape of each aperture.
 2. A connector according to claim 1 whereinsaid at least one load bearing filament is laid along said predefinedcircuitous path via embroidery.
 3. A connector according to claim 1wherein said backing sheet comprises at least one of an embroideredarticle, a knitted fabric, a woven fabric, and a plastic sheet.
 4. Aconnector according to claim 1 wherein said backing sheet is defined bya series of interconnected sewn stitches formed from said bindingfilaments.
 5. A connector according to claim 4 wherein said series ofinterconnected sewn stitches are arranged to define a backing sheet inthe form of a mesh.
 6. A connector according to claim 1 wherein saidload bearing filament extends along said circuitous path for a pluralityof circuits to define multiple strands of said load bearing filamentextending between and around each of the apertures of said pair ofapertures.
 7. A connector according to claim 1 wherein three or moreapertures are provided and wherein said circuitous path along which saidload bearing filament is laid defines chain links of said load bearingfilament which connect pairs of said apertures.
 8. A connector accordingto claim 1 wherein at least one of said binding filament and said loadbearing filament is a textile yarn.
 9. A connector according to claim 8wherein said load bearing filament is a textile suture thread of adiametric size between 0.2 to 0.5 mm.
 10. A connector according to claim8 wherein said binding filament is a textile suture thread of adiametric size between 0.1 to 0.2 mm.
 11. A connector according to claim1 wherein said multiple strands defined by the load bearing filamentcomprise between 2 to 15 strands.
 12. A connector according to claim 1wherein said load bearing filament is a wire formed from a shape-memoryalloy.
 13. A connector according to claim 1 including a pulling tail orcord.
 14. A connector according to claim 1 wherein said aperture formingmultiple strands extend completely around each aperture.
 15. A connectoraccording to claim 1 wherein said fastener comprises a screw.
 16. Aconnector according to claim 1 wherein said binding filaments extendabout at least the outer periphery of said apertures.
 17. A connectoraccording to claim 16 wherein said binding filaments extend about theentire periphery of said apertures.
 18. A connector according to claim 1wherein at least one of said load bearing filament and said bindingfilament is constructed from polyester, polypropylene, polyethylene,polyamide, polylactic acid, and alginate fibers.
 19. A connectoraccording to claim 1 wherein said load bearing filament is constructedfrom at least one of polyester, polypropylene, polyethylene, polyamide,polylactic acid, alginate fibers, metal fibers, aramid fibers, and glassstrands.